TransitionGroup errors if there are other children in addition to v-for

[jonaskuske]

Version

3.0.0-beta.4

Reproduction link

https://codepen.io/21stCenturyJonas/pen/QWjpJWm

Steps to reproduce

1. Check the console
2. Click shuffle

What is expected?

Vue renders without a warning. When the shuffle button is clicked, the elements are reordered.

What is actually happening?

Vue immediately warns, even though all children are keyed:

[Vue warn]: <TransitionGroup> children must be keyed. 
  at <Anonymous> 
  at <App>

When I click shuffle, it errors:

[Vue warn]: Unhandled error during execution of render function 
  at <Anonymous> 
  at <App>

TypeError: child.el.getBoundingClientRect is not a function
    at Proxy.<anonymous> (vue.esm-browser.js:11116)
    at renderComponentRoot (vue.esm-browser.js:5002)
    at componentEffect (vue.esm-browser.js:7729)
    at reactiveEffect (vue.esm-browser.js:3967)
    at callWithErrorHandling (vue.esm-browser.js:4807)
    at flushJobs (vue.esm-browser.js:4949)

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If "other node" is removed or commented out, everything works as expected.